"It was amazing to be able to watch a bit of history unfold live in the courtroom today," Baldwin said.

Baldwin said she wanted to appreciate the historic nature of the day. On Twitter, she had posted a photo of herself walking into the Supreme Court. And minutes after she left the court, she talked with WISN 12 News reporter Kent Wainscott from her Senate office building about her personal reaction to what she had witnessed.

"It's personal on all sorts of levels, whether it's because of my status as the first openly gay member of the U.S. Senate or because of my training as an attorney and having studied some of the cases that were cited in court today," Baldwin said.

"This is a state in which voters several years ago voted overwhelmingly to ban same-sex marriage. So if the court issues a ruling that trumps the Wisconsin Constitution and that decision by Wisconsin voters, what do you say to voters, and what do you expect the reaction to be?" Wainscott asked.

"Well, I'd say a couple of things. One of the issues that came up repeatedly in court today was how much opinions and attitudes have changed on the issue of marriage equality in recent years," Baldwin said. "There's also a responsibility of the court not just to follow the majority opinion all the time when it comes to minority rights. Both of these cases are, in my mind, about the United States becoming more equal, not less," Baldwin said.

The senator told Wainscott she was struck by the mood in the room -- the formality of the Supreme Court, but with several lighthearted moments during the oral arguments.

Still, she said, no one lost track of the seriousness of matter.

Baldwin told Wainscott she kept a close eye on their reactions and the questions they asked, but she wouldn't try to guess how they might rule.